The BBC's James Rogers in Gaza says Israel wants to try and weaken Palestinians militants as much as possible before the planned withdrawal.

But Israeli government spokesman Avi Pazner said the operation had "nothing to do with any future plan about Gaza".

"Terrorism is pouring out of this refugee camp [al-Bureij], and we have to stop it," Mr Pazner said. "We believe that by doing so we have prevented acts of terror in Israel and saved many human lives."

Palestinian militants have threatened to exact a "painful revenge".

'Failed attack'

Up to six Palestinians were killed and about 20 wounded in an attack on the main crossing point between the Gaza Strip and Israel on Saturday.

Palestinian witnesses say two jeeps disguised as Israeli military vehicles drove up to Erez crossing point.

One exploded near a Palestinian checkpoint, killing the driver and two Palestinian police. The other reached the Israeli position before exploding.

An Israeli army spokesman described the blast as a suicide bomb that went off prematurely. There were no Israeli casualties.

The militant groups Hamas, Islamic Jihad, and the al-Aqsa Martyrs Brigades, say they carried out the attack, calling it a joint "self-sacrifice operation" in a message posted on the Hamas website.